We are currently seeing — or, at least, until this week, we had seen — an all-time low of Covid-19 vaccine hesitancy: According to the Kaiser Family Foundation, the percentage of Americans who planned to wait to get a Covid-19 vaccine had dropped from 39 percent in December to 17 percent in late March. Those who say they won’t ever get it — unless, perhaps, it’s required — has, over the same period, remained fairly constant at 20 percent or just over.
The news on Tuesday that the Food and Drug Administration and the Centers for Disease Control and Prevention were recommending a several day “pause” in the administration of the Johnson & Johnson Covid-19 vaccine to give them time to investigate a potential link between the vaccine and six cases of rare blood clots may complicate that picture.
Over the last few years, people’s trust in government agencies has been eroded. Since the pandemic, our trust in public health has dropped from what were already low levels compared to other countries — even as we clapped for doctors and called nurses and other front-line health care workers heroes. We have also started to see more deserved coverage of health inequalities and systemic injustice in the health care system, which likely contributes to that lack of trust. The anti-vax movement has been eroding public trust in vaccines for years, which has led to resurgences of previously eliminated diseases like measles.
All of these factors make it difficult for people to dispassionately assess the Covid-19 vaccines and their own individual risk.
The drawback of this flurry of news coverage is that vaccine hesitancy may begin to grow again.
There is a long road for public health professions to walk until the United States gets to a place where all people have access to good health and good health care, and thus trust in our system. However, at this time, the American people have unprecedented access to a free preventive intervention that is highly effective at preventing severe disease and death from a highly infectious disease. We need better communication on risk assessment, but we also need to understand that nuance is important in these conversations.
Cerebral venous sinus thrombosis is one of the type of clots that medical professionals are concerned about in regard to the AstraZeneca and Johnson & Johnson Covid-19 vaccines.
As of April 4, there had been 222 cases of blood clotting identified in the 30-country European Economic Area plus Britain possibly linked to the AstraZeneca Covid-19 vaccine; approximately 34 million people had received that shot, The New York Times reported. Authorities in the E.U. had done detailed reviews of 86 of those cases, 18 of which were fatal, as of March 22.
In the U.S., there are currently six cases identified — one of which was fatal — out of 6.8 million people who received the shot before the pause. All cases in the U.S. involve women between 18 and 48 years old, and they developed symptoms within a defined time period — about two weeks — after getting the Johnson & Johnson vaccine.
We need better communication on risk assessment, but we also need to understand that nuance is important in these conversations.
(The mRNA vaccine types — those made by Moderna and Pfizer — don’t seem to have any excess risk of blood clots, though there have been a small number of cases reported.)
The major worry from public health officials and doctors with the potential Johnson & Johnson vaccine complication right now is that standard of care for clots — heparin therapy — might actually make the outcomes worse for patients. The number of cases might be more common than the usual incidence of these clots in the general population, but the only way to tell is to do further research.
These types of clots do happen more often in women than in the general population, partially because one of the risk factors is estrogen, either from hormonal birth control — about 15 percent of women ages 15 to 49 use a hormonal birth control method, according to the CDC — pregnancy or naturally occurring hormone levels. A large percentage of the population of the U.S. still uses tobacco products — approximately 14 percent of adults smoked cigarettes in 2019, according to the CDC. There are also several genetic conditions that make one predisposed for CVST, and most people do not know their own susceptibility.
How these and other behavioral risk factors might interact together in relation to blood clots is already a difficult question to answer, before one even begins to take into account the Covid-19 vaccine.
While CVSTs are unusual, it is still unclear if the vaccines are causing them. Adverse events happen after we take medication or get vaccinated and, in some cases, they are a coincidence. As well, when any medical intervention is introduced to a larger population after clinical trials are completed, more rare adverse events start to show up. That is why comparing the rates of these events between those who have been vaccinated and the general population is an important analysis. Very rare events are quite difficult to study, because it is hard to find large numbers of people who have these events, especially when they are of limited duration. Also, to establish causation, several criteria have to be met — like the strength of association, timing, a dose-response relationship, biological plausibility and others.
When we make individual decisions for our own health, we all have to consider a balance of risks and benefits.
Another problem in studying these cases is that women are often excluded from clinical trials, making it difficult to look at adverse events that only occur in women after the trials have ended or to determine whether the shots are at fault. (For example, pregnant and breastfeeding people were excluded from Covid-19 vaccine trials, which led to confusion about whether they should even get the Covid-19 vaccine.)
The regulatory and public health agencies in Europe and the U.S. thus paused administration of first the AstraZeneca and now the Johnson & Johnson vaccines. In E.U. and U.K., regulators have since decided that the risk of blood clots is still extremely small and administration of vaccines can continue, though they have recommended that healthy people under 30 who are not at risk for severe Covid-19 be offered a different type of vaccine where possible.
The benefit of pausing administration of the Johnson & Johnson vaccine in the U.S. while agencies look over the evidence is that we are being cautious about this possible association, which could ostensibly build confidence in the system. But the drawback of this flurry of news coverage is that vaccine hesitancy may begin to grow again.
That is what we saw in Europe: Though regulators ultimately found that the risk of blood clots was very low and the AstraZeneca vaccine was safe (especially compared to the risk of contracting Covid-19), a March poll by YouGov suggested the news coverage drove the increasing perception in France, Germany, Italy and Spain that the AstraZeneca vaccine was unsafe. In Poland, where it’s almost the only option, a recent poll showed that more than 95 percent of people would choose any other vaccine if they could.
When we make individual decisions for our own health, we all have to consider a balance of risks and benefits. Genetic and behavioral factors can cause blood clots — even in young healthy individuals. And, perhaps lost in some of the vaccine controversy, is the fact that Covid-19 is known to cause blood clots, too — some quite catastrophic. The risk of the disease, at this point, outweighs the risk of the vaccine.
I know precisely how dangerous and scary a CVST can be: One evening when I was 27, I had a sudden thunderclap headache. I went home, lost consciousness, came to, threw up from the pain and repeated that cycle until morning, when my work colleagues called to see why I wasn't at work. They called 911, EMTs brought me to a hospital and I received a diagnosis of CVST. In the hospital, I got heparin therapy and eventually improved — but only after a 10-day stay in the hospital, which included several days in the ICU, many months of anticoagulation therapies and careful monitoring. Doctors eventually determined that mine was the result of a combination of three risk factors: my genes (and, specifically, the factor 2 prothrombin gene mutation), hormonal birth control and smoking.
We won't have a complete answer about blood clots and Covid-19 vaccines for quite a while, because it takes a long time to say something about causality with any certainty. In the coming months and years, though, we will understand the possible relationship between all of these risk factors more.
Meanwhile, consider your own risks, as far as you know them. What is your risk for getting Covid-19? What is your risk for severe disease? What is your normal underlying risk for blood clots? What are some behavioral risk factors (like taking hormonal birth control)?
And if you were going to get a vaccine before this news, go ahead and get it. Pay attention and seek medical help if you develop severe headaches, shortness of breath and pain in the legs within about two weeks of having gotten a Johnson & Johnson Covid-19 vaccine, as those are all symptoms of blood clots. Look for guidance from public health agencies in the next few days — and try not to let the fear of the unknown outweigh your good judgement about what we do know.